SEOUL, South Korea >> South Korea’s military detected an “unidentified object” flying near the border with North Korea on Monday, officials said, a day after U.S. President Donald Trump and North Korean leader Kim Jong Un met at the border and agreed to resume diplomacy.

It wasn’t immediately known what the object was, but the development was a reminder of persistent tensions at the Demilitarized Zone, which bisects the two Koreas and is the world’s mostly heavily fortified border.

The South’s Joint Chiefs of Staff said in a statement that its radar found “the traces of flight by an unidentified object” over the central portion of the DMZ. It gave no further details.

South Korea’s Yonhap News Agency, citing unidentified military officials, said the object showed a flight trace that a helicopter could display and that it flew from north to south across the DMZ’s military demarcation line. Yonhap said South Korea launched fighter jets and helicopters in response.

South Korea’s Defense Ministry said it couldn’t immediately confirm the Yonhap report.

The DMZ, which was created after fighting ended in the 1950-53 Korean War, is peppered with an estimated 2 million mines and guarded by combat troops, razor wire fences, anti-tank traps and guard posts on both sides. The two Koreas have occasionally traded exchanges of gunfire there, though animosities have eased since North Korea entered talks on its nuclear program.

Sunday’s meeting between Trump and Kim, their third, took place at the border village of Panmunjom. Trump stepped across Panmunjom’s military demarcation line into North Korea with Kim, becoming the first sitting U.S. president to set foot in North Korea. He and Kim then turned back to Panmunjom’s southern part before sitting down for a meeting.

Trump announced afterward that the two nations had agreed to resume talks in the coming weeks.

Earlier Monday, South Korea’s government said it hopes the diplomatic momentum created by the latest Trump-Kim meeting would help revive inter-Korean dialogue and engagement that stopped amid an impasse in nuclear negotiations between Washington and Pyongyang.

North Korea’s state media described Kim’s meeting with Trump as “an amazing event.”

North Korea significantly reduced diplomatic activity and exchanges with the South following the summit between Trump and Kim in February that broke down due to disagreements over exchanging sanctions relief for disarmament. North Korea conducted tests of short-range missiles that could potentially threaten the South and demanded that Seoul break away from Washington and resume inter-Korean economic projects held back by U.S.-led sanctions against the North.